This invention relates to apparatus for sensing the distance between an elevator car and each floor as the car ascends and decends in its shaftway, and in particular, a floor distance sensor mounted on the elevator car.
As mentioned in my other application it is extremely difficult to assure repeated proper leveling of an elevator at each floor. Among the reasons for this is that as the building settles and changes size with temperature the shaft length and floor distances change. The cables that are attached to the car also stretch with age and expand and contract with temperature changes. In a typical elevator installation, as an example, a car location encoder can be driven through mechanical linkage to the car in order to detect the direction and distance the car moves in the shaft. The mechanical linkage, usually a steel tape, often stretches with age and expands and contracts with temperature changes. The coefficient of expansion for the tape typically is different from that of the structure. Hence it is widely understood that the distance between elevator floors is dynamic and this alone makes it difficult to properly position the car at each floor over the long-term. The inherent inaccuracies in the simple encoder further aggravate the problem.
Certain prior art systems utilize a mechanical model of the car and its shaft to simulate its movement. The model is connected to the car, usually through the same steel tape that drives the encoder. The model car moves simultaneously with the real car to actuate switches indicating its position with respect to the floor. In its simplest terms, this is a device having an arrangement of switches corresponding to preselected floor locations and an actuator which ascends and decends simultaneously with the car to actuate the switches. This system, however, requires constant readjustment of the switches to compensate for the changes in actual floor location due to the structural variations and the variations in the steel tape previously explained.
There are basically two reasons for requiring the precise car to floor distance. In many elevator installations, particularly high speed ones, the car doors start to open as the car approaches the floor while it is being stopped. Advanced car door opening, as this is called, minimizes the stationary car time at the floor to increase the overall system speed. In order to accomplish this as efficiently and safely as possible it is vital to know precisely when the car is within a preselected distance from the floor before starting to open car doors and slowing the car down. Ideally the doors are fully open just as the car stops at the floor level. They must not be substantially open while the car is still moving because that can be dangerous. The second reason for needing precise floor location information is simply to accomplish exact car leveling at each floor within preselected desirable ranges. Car leveling means positioning the floor of the car as close as possible to the landing floor level. Without accurate information indicating the actual location of the car with respect to the floor landing it is impossible to minimize the leveling distance. This is particularly true in systems utilizing apparatus that determine the distance between the car and the floor through mechanical connection to the car. The previously mentioned shaft encoder and also car model apparatus are examples of such apparatus.
An object of the invention is to provide combined leveling distance and stopping distance information.
In accordance with the present invention the distance to the floor is directly measured from the car by reference to the shaft near each floor. A U-shaped channel is mounted on the elevator car. On one wall of the channel illuminating devices are mounted at preselected distances apart. On the opposite wall there are mounted corresponding light receivers. Each receiver is therefore on when the car is between floors. A vane is fastened to the shaft wall at a preselected distance from each floor. As the car approaches a floor the vane passes between the walls so as to turn the receivers off in succession. The combination of on and off receivers reflects the car's distance above or below floor level. One receiver is in a transition state when the car is at floor level and goes on and off as the car moves outside a preset level zone around the floor level. Hence by detecting which receivers are on and off the position of the car with respect to the floor level can be ascertained precisely. In addition movement outside the level zone can be ascertained regardless of the state of all the receivers. This provides redundancy and better overall accuracy.
Other objects, benefits and features of the invention will be apparent to one skilled in the art from the following detailed description and claims wherein: